Whipstocks are essentially long ramps that direct a milling assembly laterally into a tubular wall to form an opening referred to as a window for a lateral exit from a main bore or an existing lateral to a main bore. These whipstocks have to be properly oriented so that the mill will exit in a desired orientation into the producing or injection zone, depending on the application. Measurement while drilling or wireline gyro tools assist in the orientation of the whipstock ramp before an underlying anchor is set for fixation of the whipstock.
FIG. 1 illustrates a currently available design of a mechanically supported whipstock and anchor where the running tool engages a whipstock opening. Typically, the running tool 10 has a hook 12 that engages an opening 14 in the whipstock ramp 16. A shear pin or bolt 18 initially secures the running tool 10 to the top of the ramp 16 when running in. Running tool 10 has an extension tube 20 that runs through the whipstock body under the ramp 16 and into a seal bore 22 of a bottom sub 24 connected below the ramp 16. An anchor A is located below bottom sub 24. The procedure with this design is to cement through the anchor onto a support that exists in the borehole that is not shown to create a barrier that is requested by some operators. When cementing to create a barrier is concluded, a ball is dropped on a seat near the anchor A to set the anchor. The running tool is then released by shearing pin or bolt 18 by setting down weight against the set anchor to get the hook 12 out of opening 14 in ramp 16 followed by rotating before pulling out of the hole with the running tool 10 so as to avoid re-engaging the hook 12 in the opening 14 on the way out of the hole.
There are several limitations in this process. One is that the running tool 10 may be positioned in a highly deviated portion of a borehole making rotation difficult and further reducing surface feedback as to how much rotation has actually taken place at the hook 12 with a given amount of rotation at the surface. In a deviated borehole, rubbing on the wall can result in far less rotation at a downhole end of a string than the rotation applied at the surface. The other issue is that since the attempt to release the running tool 10 happens after cementing, there are concerns that the extension tube 20 may not come out of the anchor A. Another concern may be that in trying to set the anchor with a ball landed on a seat after cementing there may be an issue of getting a good enough seal on the ball to the seat to set the anchor A as there may be residual cement on the seat from the cementing step that preceded setting the anchor.
Generally relevant to the setting or retrieving of whipstocks and the use of running tools for whipstocks are: U.S. Pat. No. 5,909,770; U.S. Pat. No. 7,373,984; U.S. Pat. No. 8,490,697 and U.S. Pat. No. 5,549,163.
The present invention makes it possible to release the running tool before cementing. The running tool is released hydraulically rather than mechanically so rotation for release is not needed. The running tool is dovetailed to the whipstock ramp so that downward force and torque can be transmitted to the whipstock from the running tool without concern of the two becoming disengaged. The placement of the running tool components in position for cementing accomplishes the running tool release before the cement is pumped. The running tool can initially deliver uphole force to the whipstock when being positioned or when running in. In a more specific example the shifting of a ball seat in the running tool removes support for a collet that connect the running tool to the whipstock while at the same time opening a cement passage around a seated ball and through the ball seat to deliver cement through the already set anchor that has had a passage through it opened up as the anchor was set. The above are some aspects of the present invention but those skilled in the art will appreciate additional features from a review of the detailed description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.